How to Measure the Ripple and Noise Index of a DC Power Supply
The ripple and noise of DC power supply are important parameters for evaluating the quality of power supply, which reflect the instability and interference of power output. Large ripples or noise may cause unstable system operation, increased sensor errors, analog signal distortion, and other issues. Therefore, it is very important to correctly measure and evaluate ripple and noise levels when designing and selecting power supplies. This article will introduce how to test the ripple and noise of DC power supplies, and provide corresponding measurement methods and techniques. The AC stray components of DC power output are called ripple and noise, or periodic and random deviation (PARD), which are parameters describing the quality of the power supply. The measured values are true effective value (RMS) or peak to peak value (Vpp), usually specified in the bandwidth range of 20Hz~20MHz, reflecting the instability and interference in the power output. However, their specific definitions and characteristics differ slightly
Power Ripple
Power ripple refers to the periodic changes or fluctuations present in the power output, as shown in Figure 1. It usually exists in the form of an AC signal in the output of a DC power supply. Power ripple can be caused by factors such as power supply design, power filters, and may also be affected by load changes or other external disturbances. The frequency of power ripple is usually related to the input frequency of the power supply, such as the ripple frequency of AC power supply being 50Hz or 60Hz.
